Cycle of decline
Estimate portends big changes in makeup of forests
Lovers of the local high country could find a recent projection of a warming world’s impacts on area forests to be chilling.
By 2060, according to a U.S. Forest Service estimate, almost all of the Uncompahgre Plateau would no longer be able to sustain growth of new aspen and spruce, meaning that the plateau could be virtually aspen- and spruce-free by century’s end after the remaining trees die.
On the southern and eastern fringes of Grand Mesa, aspen also could see sizable losses of suitable habitat by 2060, with spruce habitat largely slipping into a threatened category across the mesa, meaning the future climate isn’t favorable to sustaining it.
The mapped projections were made by the Forest Service in connection with a planning project for spruce and aspen logging and other treatments for coming years on the Grand Mesa, Uncompahgre and Gunnison national forests.
“They’re kind of terrifying,” Ted Zukoski, an attorney with the conservation group Earthjustice, said of the Forest Service maps.
The modeling used by the Forest Service found that 52 percent of current aspen distribution across the forests would be in the lost habitat category by 2060, and 42 percent in the threatened category, “meaning it is conceivable that 94 (percent) of current aspen distribution may not continue into the next century,” the Forest Service says in its final environmental impact statement for the project, released earlier this year.
Aspen habitat generally would be lost at low elevations, especially on south-facing slopes, with the western West Elks also sharing in that habitat loss. Some of that habitat loss could be offset by newly emerging habitat at higher elevations. But Samantha Staley, a Forest Service planner, says while the climate may shift to support the species at a higher elevation, that doesn’t mean that other ecological components necessary to support the species will be present. Some higher elevations may not be suitable thanks to things such as poor soil conditions or rocky scree slopes.
The model projects a 22 percent loss of current spruce distribution, and that 58 percent of distribution will become threatened, meaning that 80 percent of current distribution may not continue into the next century. Areas of substantial loss beyond the Uncompahgre Plateau could occur in the West Elk Mountains, east of Grand Mesa, and south of the Black Canyon/Blue Mesa Reservoir, the Forest Service impact statement says.
The model is based on an assumption of a continuing warming trend on the forests. The statement says temperatures are expected to rise 5.4 to 7 degrees by 2040-60. Higher temperatures could foster more spruce beetle outbreaks, further stress trees because of increased drought and result in more damage from wildfire.
“I think what those maps show is stunning,” Zukoski said. “… I think those kind of maps are extremely helpful because they permit people to see in their areas, places that they care about in their backyards, what the world’s going to be like for their kids and grandkids, and for themselves if they live long enough.
“I think giving people that picture over that longer term really helps them understand how dramatic the impacts of climate change could be if we don’t work darn hard to get a handle on it.”
Staley has worked as a Forest Service co-leader on the forests’ aspen and spruce treatment planning project, known as the Spruce Beetle Epidemic and Aspen Decline Management Response. She said the drought in the early 2000s precipitated epidemics on the forests that have affected about a third of its spruce and aspen.
Meanwhile, a 2006 model created by researchers led by Gerald Rehfeldt, who worked at the Forest Service’s Moscow Forestry Sciences Laboratory in Idaho before retiring, projected a 47 percent drop in suitable spruce habitat in the western United States in the decade around 2060, and a 72 percent loss by 2090.
The Forest Service statement says that for the forests, that model was rebuilt using local data, more “topographical predictors,” newer global climate models and carbon scenarios, and higher-resolution climate data. Its resulting projections are an average from three climate models and three greenhouse gas emission scenarios.
“These are models, which necessarily include some amount of error,” Staley said.
She said it’s based on the best available information today, and the Forest Service understands the science will be a lot better in a decade.
“We have to look at it as it’s not the gospel, but it’s the best available scientific information that we have today about where vegetation may be headed in the future,” Staley said.
Jim Worrall, a forest pathologist with the Forest Service’s Rocky Mountain Region 2, which includes Colorado, said Rehfeldt worked with him and others to localize his methods, and they developed a model for 13 tree species in southwest Colorado, including spruce and aspen.
Worrall said one of the biggest uncertainties pertains to the climate models, because there are so many models and carbon scenarios to choose from. He said the forest-habitat predictions the Forest Service came up with concern him and he hopes they’re wrong, but they’re the best idea researchers now have of what the future holds.
“It’s really a very objective process. There’s really no subjectivity in the model development,” he said.
Interpreting the results to make them simple and easy to digest can be a little subjective, he said.
“But we’ve been pretty conservative in that,” he said, adding that the predictions are based on what the models are telling researchers, and those models are built on a lot of data.
Staley said the agency is compelled to use that science in its planning and efforts to manage sustainably into the future, and current research acknowledges that warming will result in shifting of not just animals but trees in terms of habitat.
“The environment is changing and that’s why we’re using as much information as we can to make the best decisions,” she said.
Forests are always changing, thanks to factors such as insect infestation and wildfire, and cycles such as aspen thriving first in disturbed areas and later being succeeded by other types of trees. But now the Forest Service is learning more about how that’s happening in the context of “pretty rapid climate change,” and what the forest may look like in that context, Staley said.
While every generation sees a slightly different version of a forest, future forests may be ones that people have never seen locally, she said. Rather than a mid-elevation forest shifting back and forth from aspen to spruce, it may shift to oakbrush.
“And that’s a new shift,” she said.
Oakbrush and mixed-mountain shrubs cover about a quarter of the Uncompahgre Plateau now.
ASPEN, SPRUCE ROLES
The impact statement calls aspen a “keystone” species. Aspen forests attract everything from elk to birds and small animals, foster luxuriant growth of herbs and shrubs, improve streamflow and water movement, can have logging value and also are valued for their beauty and tourism value.
Spruce are an important timber source, provide shade and shelter that helps slow spring snowmelt and runoff from rainstorms, and are valued by a range of recreationists and for their scenic value, the Forest Service statement says. In the forests, spruce provide important habitat for the Canada lynx, listed for protection under the Endangered Species Act, and other species either listed or being considered for listing.
Norm Birtcher is a forester for Montrose Forest Products, a local mill that expects to benefit from some of the logging projects contemplated by the Forest Service in coming years.
He said of future forest modeling, “It’s very difficult to predict (based) on climate. Climate has always changed in the past and it will change in the future. None of the models are correct. They try to be as good as they can.”
He said with aspen being so prevalent on the Uncompahgre Plateau, some spruce that is lost there will likely be replaced by aspen.
The forest will respond to climate and other influences, “but I don’t think we need to be overly alarmed by it,” he said.
CONTRADICTION ON COAL?
Zukoski sees a contradiction in the fact that the Forest Service is looking at ways of spending taxpayer money on its forests’ aspen and spruce project to try to limit the impacts of climate change in the region (see related story, page 4A) even as it is seeking to reinstate the North Fork Valley coal mining exemption to the Colorado roadless rule. That exemption, vacated by a court ruling, could allow for the mining of some 170 million tons of coal, which would further worsen climate change, Zukoski said. That’s because of the carbon emissions that would come from burning it and the methane emissions that would result from mining it.
The Forest Service has said its forests treatment project could have a $34.7 million to $44.2 million discounted cost to the government.
Responding to Zukoski’s criticism, Staley points to the Forest Service’s enabling legislation obligating it to manage for multiple uses and resources.
“I don’t know that it’s a new thing that on one hand we’re trying to balance this use and impact over here, and this other use and this impact over there. It’s part of the job,” she said.
Zukoski said he would assume that the kind of climate-change forest impacts modeled for the forests might be similar across the state. Worrall said that was generally the case for the agency’s modeling across southwest Colorado. But the projected impacts were generally worse farther west where elevations are lower, with less severe impacts in high country that could even see some increased suitability for trees like aspen at higher elevations.
He said of the modeling’s findings, “I think we need to plan for the worst and hope for the best, is what I suggest. But most likely even if the models are a little off, we’re going to be looking at very different conditions in the future for our children and our children’s children than we have now.”